PTO clutch is held on with a single bolt that us fairly deep so you might need a deep walled socket to get on to it.
A rattle gun is you best friend, they come off easily then you pull the seal out with a pick being carefull not to dig into the wall of the crankcase.
I have even seen people put some self tappers in there and then use a claw hammer or wrecking bar to lever them out by the heads.
Take a few photos of the area before you start pulling the seal and post them here.
That oil seal rarely gives problems.
Before you start grab the pto and see if you can move it up & down. If you can there is serious damage to the engine.
Go to Cub cadet .com and download your exploded parts diagram is you want to see exactly how it all goes together.
Troll around the link below and you will find your engine repair manual
http://www.mymowerparts.com/pdf/